Florida Keys National Marine Sanctuary

Acid bath. Scientists are beginning to test how marine organisms, such as these corals, will respond to the increasingly acidic conditions created by the ocean's absorption of carbon dioxide.

As Field Matures, Ocean Acidification Scientists Face New Challenges

David is a Deputy News Editor specializing in coverage of science policy, energy and the environment.

MONTEREY, CALIFORNIA—Ocean acidification research is getting a bit more competitive for Jean-Pierre Gattuso, and he likes it that way. Nearly 15 years ago, the biogeochemist at the French National Center for Scientific Research in Villefranche-sur-mer was one of just a handful of scientists worldwide examining how the buildup of carbon dioxide in the atmosphere might affect sea life by altering the chemistry of the oceans. When he published his first paper on the topic in 1998, few scientists were interested. "It just wasn't a hot topic," he says, adding that he was able to work at a leisurely pace. That first paper, for instance, took 4 years to go from experiment to publication. Gattuso didn't worry that someone else might publish similar results first.

These days, however, "the field is much bigger and more competitive," Gattuso says. In 2004, researchers were publishing just 20 papers a year on ocean acidification, he notes, and just 125 researchers from 20 nations showed up for the first major international meeting on the subject in Paris (which was held in a single room). This year, journals expect to publish more than 300 papers on the issue. And more than 550 researchers from 40 nations have gathered here on the coast of California for the Third International Symposium on the Ocean in a High CO2 World, which opened yesterday at a sprawling, multiroom conference center. "There has been remarkable growth in a very short time," Gattuso says.

That growth is on full display at the conference. It includes hundreds of presentations on the biological implications of the ocean's absorption of increasing quantities of atmospheric carbon dioxide. The resulting chemical reactions are shifting the pH of seawater toward the acidic end of the scale. On average, researchers estimate that surface waters have seen a 0.1 decrease in pH over the past century or so; that's a remarkably rapid 30% increase in acidity.

Here, researchers are discussing a wide range of effects, including how increasingly acidic waters can influence something as small as the function of a single gene, or as big as the structure of a vast coastal ecosystem. Taken together, the talks highlight an evolving and increasingly nuanced view of acidification's potential impacts, researchers say. Not long ago, for instance, many researchers feared that most shell-building organisms, such as oysters, crabs, and shrimp, might not be able to withstand more acidic waters, which can dissolve the calcium carbonate used to build shells. "There was the idea that calcifiers were doomed," says biologist Sam Dupont of the University of Gothenburg, Kristineberg, in Fiskebäckskil, Sweden. But work that he and others are presenting at the conference suggests that some shell-builders can cope with acidification. Other researchers will show that even seemingly similar species or populations can have very different responses, suggesting there will be losers and winners in an acidified ocean. "We're seeing some hope" that some organisms will be able to adapt, Dupont says.

The conference also highlights the changing focus of acidification studies -- and a growing feeling that, despite continued uncertainty, scientists have learned enough to urge policymakers to take action. Historically, researchers "took a very geochemical view" of acidification, "but now we're beginning to take a more biological view," says marine scientist Joanie Kleypas of the National Center for Atmospheric Research in Boulder, Colorado. That means studying not only how specific organisms respond to changes in acidity, but also how changes in seawater pH can effect things like metabolism, reproduction, and even behavior. Such basic studies "will help us understand the underlying mechanisms that drive general responses to acidification," so researchers can forego taking on the impossible task of testing thousands of individual species, says coral scientist Chris Langdon of the University of Miami in Florida.

Another needed step, he and others say, is to understand how shifts at the individual or species level—such as the rise or fall of a group of plankton at the base of a food chain—might ripple through an entire ecosystem. Researchers including Langdon are also starting to study how several factors—such as rising sea temperatures plus increasing acidity—might combine to deliver a "double punch" to marine ecosystems.

A long-term dream, Gattuso says, is to set up large experiments in which scientists can artificially increase acidity levels in curtained-off chunks of the natural ocean, and then watch what happens over years, instead of the days or months currently possible in smaller prototypes. Ecologists who study terrestrial ecosystems are already running similar big manipulation experiments on land, he notes, including studies that pump extra carbon dioxide into forests, grasslands, and marshes. But marine scientists face numerous technical challenges in replicating such controlled studies in the sea, not to mention the difficulty of finding the money. Still, short-term acidification experiments risk over- or underestimating the true effects, Gattuso says, so "anything we can do to make experiments in more realistic, natural conditions would be very helpful."

Policymakers, however, shouldn't wait for the results from such studies to address the risks posed by acidification, he and other researchers say. In the long term, that means reaching a global deal to reduce emissions of carbon dioxide. In the shorter term, however, the researchers say that local and national governments can take steps now to reduce other problems, such as nutrient pollution in coastal areas, which can multiply the problems created by acidification. "Yes, we are seeing variability and uncertainty" in acidification's biological impacts, he says. "But even I have been surprised at just how pervasive the effects are. We now know enough to know that there is urgency to act."

Scientists will get a chance to deliver that message in person on Thursday, when a host of political figures will visit the conference. Those expected to attend include Jane Lubchenco, head of the U.S. National Oceanic and Atmospheric Administration, Prince Albert II of Monaco, and U.S. Representative Sam Farr (D-CA).

Posted in Earth, Environment